This study explored the contribution of peer-assisted learning (PAL) in the development of evaluative judgement capacity; the ability to understand work quality and apply those standards to appraising performance. The study employed a mixed methods approach, collecting self-reported survey data, observations of, and reflective interviews with, the medical students observed. Participants were in their first year of clinical placements. Data were thematically analysed. Students indicated that PAL contributed to both the comprehension of notions of quality, and the practice of making comparisons between a given performance and the standards. Emergent themes included peer story-telling, direct observation of performance, and peer-based feedback, all of which helped students to define "work quality". By participating in PAL, students were required to make comparisons, therefore using the standards of practice and gaining a deeper understanding of them. The data revealed tensions in that peers were seen as less threatening than supervisors with the advantage of increasing learners' appetites for thoughtful "intellectual risk taking". Despite this reported advantage of peer engagement, learners still expressed a preference for feedback from senior teachers as more trusted sources of clinical knowledge. While this study suggests that PAL already contributes to the development of evaluative judgement, further steps could be taken to formalise PAL in clinical placements to improve learners' capacity to make accurate judgements on the performance of self and others. Further experimental studies are necessary to confirm the best methods of using PAL to develop evaluative judgement. This may include both students and educators as instigators of PAL in the workplace.